3 0 6 D O C U M E N T 3 1 5 N O V E M B E R 1 9 2 8 315. From Rudolf Goldschmidt Berlin, 15 November 1928 Dear Professor Einstein, I would like to make some comments on your idea, which we can best discuss in detail in person that would greatly please me. Your idea. Suggested changes: a) Almost completely closed ring for the magnetic field pro- duced by C, by suspending B at F instead of at C. b) Replacing the joint, which even in the case of an excellent point suspension could be a source of trouble, by a spring- loaded clamping of B at the point F. The iron in B will otherwise not be maintained in a stable position midway be- tween the two poles, but rather will always be pulled to the one pole or the other [English: freezing = anfrieren].[2] An elastic force must be provided to prevent that [English: restoring force]. B will have to be very stiff, with a high resonant frequen- cy, to avoid unwanted resonances. The spring-loading of B will need to be placed very close to the suspension F, and its cross-section must have a shape like , in order to prevent higher-harmonic oscillations from occurring. (Separation of the mass and the elastic elements instead of distributing them along its length). The elasticity of the acoustic horn cannot be used to pro- vide the restoring force that would be too unpredictable. 3.) Advantages: a) A relatively small mass of the tongue B, since the perma- nent magnetism just “passes through” it, and B need not guide it at any point along its length. [1] [3]